The present invention relates to aquatic recreational devices. More particularly, the invention concerns a hand-launchable projectile that has hydrodynamic properties suitable for controllable, sustainable, long-distance submarine travel.
For millennia, small hand-launched inert (i.e. non-motile) projectiles have been the central object employed in athletic games and sports events. Examples of such games popular at this time are catch, baseball, football, basketball, cricket, handball, disk-flying, boomerang-throwing, etc. In each such game, an airfoil device is passed between teams or players in such a way that points are scored or distance of travel is scored. Each of these projectiles is characterized by several aerodynamic and physical properties. In all cases the object, as it travels in air, creates a small amount of aerodynamic drag relative to the kinetic energy of the projectile. A second feature of these projectiles is their mass and size; all can be hand held and launched by the average person. To allow this to occur the projectile must be small enough to be grasped by the human hand and yet must contain enough mass that the acceleration imparted to it by the human body is maximized, i.e. its kinetic energy at launch is high. Within these constraints, the travel of the projectile will finally and dramatically be determined by its aerodynamic drag. Objects with low drag will travel long distances; those with high drag will not. Virtually all recreational projectiles fall in well-defined ranges of weight, size and aerodynamic drag.
Testimonial to the high level of evolution present in these projectiles is the fact that changes in physical properties of the media in which the projectiles operate have a profound effect on their performance. Increasing the kinematic viscosity of the fluid in which the projectile is launched will reduce the projectile's performance to the point where it is no longer useful as a throwing toy. This results from increased drag on the projectile produced by increased kinematic viscosity of the medium. One may witness this effect while attempting to throw a baseball under water. Water as a travel medium increases drag on the ball, and the ball's buoyancy elevates the ball along its submarine path. The ball's kinetic energy, and hence its travel distance, is reduced by the increased drag.